
This application is based on Patent application Ser. No. 2000-89654 filed Mar. 28, 2000 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink-jet printing apparatus, and a recovery processing method of an ejection port. More particularly, the invention relates to an ink-jet printing apparatus and a recovery processing method of an ejection port having a function for recovering or maintaining good ink ejection performance of a printing head.
2. Description of the Related Art
Associated with the proliferation of information processing equipment, printing apparatuses as peripheral equipment have also proliferated. Particularly, an ink-jet printing apparatus,which performs printing by ejecting ink droplets from a plurality of ejection openings provided in a printing head toward a printing medium, has rapidly proliferated because color printing can be performed easily. Furthermore, associated with a demand for down-sizing, there has been proposed a serial type ink-jet printing apparatus, which alternately repeats a printing operation of moving the printing head in a predetermined direction and ejecting ink droplets during movement of the printing head and a paper feeding operation for feeding the printing medium by a predetermined amount in a direction perpendicular to the motion direction of the printing head.
In such ink-jet printing apparatus, the printing head is frequently mounted on a carriage which can scan in a predetermined direction. In a case of full-color printing, each of the printing heads for respective colors of yellow, magenta, cyan and black is constructed by integrating an ejection opening array and an ink tank. Also, among the printing heads, there are some printing heads, in which only the ink tank is detachable.
On the other hand, as a color image can be easily processed by information processing equipment, there has been an increasing demand for an ink-jet printing apparatus that can readily print those images in full-color printing, with enhanced image quality. To meet the demand, there has been proposed an ink-jet printing apparatus in which high image quality is realized by printing multi-gradation levels of density using the following method.
For example, concerning magenta and cyan, two kinds of inks having mutually different densities, namely, high density ink and low density ink, are provided for dividing ink densities of image data into a greater number of gradation levels for performing printing with such high and low density inks. In the alternative, by switching the ink ejection amount to be ejected from the printing head using only one kind of ink for each color, depending upon the density of the image data, to perform printing with different sizes of dots on the printing medium can realize high gradation levels and high image quality.
Particularly, the method for increasing gradation levels by forming different sizes of dots on the printing medium by switching ink ejection amounts can restrict the number of ink tanks to be loaded. Therefore, such method is effective for down-sizing of ink tanks and down-sizing of the ink-jet printing apparatus.
The printing head switching the ink ejection amount has been disclosed in Japanese Patent Application Laid-open No. 9-254413(1997) and Japanese Patent Application Laid-Open No. 9-48125(1997). In the above-identified publications, it has been proposed to differentiate ejection amounts by arranging a plurality of rows of ejection openings on an ink ejection face and differentiating sizes of ejection openings per row of the ejection openings.
By performing a printing operation many times or by leaving the printing head inoperative for a long period, it is possible to cause variations in ejection amount and/or ejecting direction from the printing head nozzles due to deposition of dust and dirt around the ejection opening or plugging with ink of increased density. In the alternative, ink may be dried to make ejection unstable upon initiation of printing.
In order to prevent drying of ink or ejection failure, the ink-jet printing apparatus is provided with a cap for covering the ejection opening face while the printing head is not used, or is provided with means for performing preparatory ejection at a predetermined position out of the printing region. For example, in an ink-jet printing apparatus disclosed in Japanese Patent Application Laid-open No. 10-100451(1998), a cap covering a plurality of ejection openings is provided.
On the other hand, in the case of the printing head, in which only the ink tank is detachable, when the old ink tank is removed, air may penetrate into an ink passage connecting the ink tank and the ejection opening, or air may penetrate around the ejection opening. Therefore, when the ink tank is exchanged with new ink tank, re-filling of the ink becomes necessary up to around the ejection opening. Therefore, upon exchanging the ink tank, the ejection opening face is covered with the cap to perform suction of the ink by a suction means with driving a pump.
Such recovery operation by the preparatory ejection means, suction means and so on are performed during a printing operation or a non-printing operation, or upon exchanging of the ink tank or the like.
FIGS. 8A and 8B are sections showing a printing head portion and recovery unit portion of the conventional ink-jet printing apparatus.
As shown in FIG. 8A, a printing head 83 is mounted on a head carriage frame 83a movably arranged on a pair of upper and lower guide members 82. The printing head 83 is provided with two ejection opening portions 83b and 83c projecting downwardly from the lower surface of the head carriage frame 83a, namely from a surface opposing the printing medium feeding passage, a black ink tank 83d and a color ink tank 83e arranged detachably on the head carriage frame 83a. 
The ejection opening portions 83b and 83c are formed with a plurality of ejection openings, respectively. The ejection opening portion 83b ejects black ink supplied from the black ink tank 83d and the ejection opening portion 83c ejects three kinds of inks of cyan, magenta and yellow supplied from the color ink tank 83e. 
It should be noted that the black ink ejection openings 83f, the yellow ink ejection openings 83g, the magenta ink ejection openings 83h and the cyan ink ejection openings 83f are provided in plural. However, for the purpose of illustration, only one ejection opening is illustrated.
The ink-jet printing apparatus feeds a printing medium by means of a not shown printing medium feeding member, reciprocally scans the printing head and ejects ink droplets from respective ejection openings to form a desired image on the printing medium.
As shown in FIG. 8B, a recovery unit 810 for providing recovery process for the printing head 83 is provided. To the recovery unit 810, caps 89b and 89c for covering the ejection openings 83b and 83c are provided. The caps 89b and 89c are connected to not shown pumps. The recovery unit 810 moves up and down to cover the ejection openings 83b and 83c with the caps 89b and 89c and performs suction recovery by the pumps.
A plurality of ejection openings are arranged on the ejection opening face of the printing head. Among the various ink-jet printing apparatuses, some of the ink-jet printing apparatuses have ejection openings that are not uniform size and rather differentiate per row of ejection openings to permit printing of an image at higher resolution. When a plurality of kinds of ejection openings of different shapes are present, the conventional ink-jet printing apparatus is provided with the caps in a number corresponding to shapes and kinds of the ejection openings, which requires a large space and hinders down-sizing of the overall apparatus. On the other hand, when an attempt is made to perform suction recovery for all the ejection openings with one cap, fluctuations in suction may result due to differences of flow resistance of the ink caused by the shape of the ejection openings.
More particularly, the row of the ejection openings having high flow resistance lacks ink suction force if the same suction force is applied in comparison with the row of the ejection openings having low flow resistance upon cap suction to make it impossible to effectively perform suction recovery. In order to perform suction for the row of the ejection openings having high flow resistance, a long period of suction operation is required, or the ink of increased viscosity plugging the ejection openings cannot be suctioned satisfactorily. On the other hand, from the row of the ejection openings having low flow resistance is suctioned an unnecessarily large amount of ink if the same suction process as that for the ejection openings having high flow resistance is performed, resulting in a waste of ink. Furthermore, excessive suction may cause retention of bubbles within the ejection opening to possibly make normal ink ejection impossible.
The present invention has been achieved for solving the problems in the prior art. Therefore, the present invention can provide an ink-jet printing apparatus and a recovery processing method of an ejection port which can satisfactorily perform a recovery process for respective ejection openings having different ink flow resistances and permit down-sizing.
According to one aspect of the present invention, an ink-jet printing apparatus including a printing head having a plurality of ejection openings and a cap covering the ejection opening face where a plurality of ejection openings of the printing head is arranged, and suction means suctioning ink from the ejection openings covered by the cap, comprises a sealing member being provided within the cap for sealing a portion of the plurality of ejection openings. In the ink-jet printing apparatus, when the of the plurality of ejection openings are sealed by the sealing member, an operation for suctioning ink from the ejection openings which are not sealed is performed by the suction means.
According to another aspect of the present invention, an ink-jet printing apparatus has a cap for covering an ejection opening face of a printing head in which a plurality of ejection openings are arranged, wherein the cap comprises a projecting lip portion surrounding a plurality of ejection openings when the cap covers the ejection opening face and a projecting portion formed inside surrounded by the lip portion and sealing a portion of the plurality of ejection openings, and wherein when the lip portion contacts with the ejection opening face at a predetermined position, the projecting portion seals the portion of ejection openings, and when the cap moves in a direction parallel to the ejection opening face to contact the ejection opening face at a position different from the predetermined position, the projecting portion does not seal the portion of ejection openings.
According to another aspect of the present invention, an ink-jet printing apparatus has a cap for covering an ejection opening face of a printing head in which a plurality of ejection openings are arranged, wherein the cap comprises a projecting lip portion surrounding a plurality of ejection openings when the cap covers the ejection opening face, a deformable lip portion formed at the projecting tip end of the lip portion, and a projecting portion formed inside surrounded by the lip portion and sealing a portion of the plurality of ejection openings, and wherein when the lip portion is applied with a predetermined contact force at a predetermined position to contact with the ejection opening face, the deformable lip portion is deformed and the projecting portion seals the portion of ejection openings, and when the lip portion is applied with a force less than the predetermined contact force at the predetermined position to contact with the ejection opening face, the deformable lip portion is not deformed and the projecting portion does not seal the portion of ejection openings.
According another aspect of the present invention, an ink-jet printing apparatus has a cap for covering an ejection opening face of an ink head in which a plurality of ejection openings are arranged, wherein the cap comprises a projecting lip portion surrounding a plurality of ejection openings when the cap covers the ejection opening face, a projecting portion formed inside surrounded by the lip portion and sealing a portion of the plurality of ejection openings, and a projecting portion actuating portion for moving the projecting portion for sealing the portion of ejection openings when a suction process of the ejection openings other than the portion of ejection openings is performed, and for moving the projecting portion for releasing the seal of the portion of ejection openings while the suction process of the portion of ejection openings is performed.
According to another aspect of the present invention, an ejection recovery processing method of an ejection port comprises a covering step of covering by a cap an ejection opening face on which is arranged a plurality of ejection openings, a sealing step of sealing a portion of the plurality of ejection openings by a sealing member provided within the cap, and a suction step of suctioning the ink from ejection openings not sealed by the sealing member in the sealing step.
By employing the above structure, upon covering the ejection opening face with the cap at the predetermined position, the projecting portion is contacted with the predetermined row of the ejection openings, such as the ejection openings having low flow resistance, to seal the predetermined row of the ejection openings. By performing suction in this condition, ink is suctioned from the row of the ejection openings other than the predetermined row of ejection openings. Then, after sufficiently suctioning the ink from the row of ejection openings other than the predetermined row of ejection openings, the cap is moved to release sealing by the projecting portion to effect suctioning. Then, ink is suctioned from the predetermined row of ejection openings. Thus, ink can be suctioned from all of the ejection openings in just proportion.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.